Schedule of Investments (Unaudited) - Treasury Bills - USD ($)		Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Fair Value	[1]	$ 91,977,743	$ 135,984,580
U.S. Treasury Bills, 0.275% due April 7, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[2],[3]	12.78%
Fair Value	[2],[3]	$ 12,999,767
Face Value	[2],[3]	$ 13,000,000
U.S. Treasury Bills, 0.200% due April 28, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]	12.77%
Fair Value	[3]	$ 12,998,388
Face Value	[3]	$ 13,000,000
U.S. Treasury Bills, 0.325% due June 2, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[2],[3]	56.00%
Fair Value	[2],[3]	$ 56,985,123
Face Value	[2],[3]	$ 57,000,000
U.S. Treasury Bills, 0.235% due July 7, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]	8.84%
Fair Value	[3]	$ 8,994,465
Face Value	[3]	$ 9,000,000
United States Treasury Obligations [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]	90.39%	119.30%	[4]
Fair Value	[3]	$ 91,977,743	$ 135,984,580	[4]
United States Treasury Obligations, cost	[3]	$ 91,962,871	$ 135,975,320	[4]
U.S. Treasury Bills, 0.205% due January 14, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		13.16%
Fair Value	[3],[4]		$ 14,999,580
Face Value	[3],[4]		$ 15,000,000
U.S. Treasury Bills, 0.195% due January 21, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		3.51%
Fair Value	[3],[4]		$ 3,999,836
Face Value	[3],[4]		$ 4,000,000
U.S. Treasury Bills, 0.170% due January 28, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		13.16%
Fair Value	[3],[4]		$ 14,998,770
Face Value	[3],[4]		$ 15,000,000
U.S. Treasury Bills, 0.135% due February 11, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		6.14%
Fair Value	[3],[4]		$ 6,999,076
Face Value	[3],[4]		$ 7,000,000
U.S. Treasury Bills, 0.145% due February 18, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		39.48%
Fair Value	[3],[4]		$ 44,994,060
Face Value	[3],[4]		$ 45,000,000
U.S. Treasury Bills, 0.140% due February 25, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		21.05%
Fair Value	[3],[4]		$ 23,997,648
Face Value	[3],[4]		$ 24,000,000
U.S. Treasury Bills, 0.215% due March 3, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		17.54%
Fair Value	[3],[4]		$ 19,996,840
Face Value	[3],[4]		$ 20,000,000
U.S. Treasury Bills, 0.280% due March 10, 2016 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[4]		5.26%
Fair Value	[3],[4]		$ 5,998,770
Face Value	[3],[4]		$ 6,000,000

[1] $63,484,032 and $33,225,157, respectively is restricted for maintenance margin purposes

[2] All or a portion of United States Treasury Obligations are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.

[3] Security may be traded on a discount basis. The interest rate shown represents the discount rate at the most recent auction date of the security prior to year end.

[4] A portion of United States Treasury Obligations are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.